"I think it's going to take aggressive leadership to restore the Air Force's reputation with regard to a whole series of things that don't really have a lot to do with nuclear weapons handling," says Tom Ehrhard, a retired Air Force colonel and now a senior fellow at the Center for Strategic and Budgetary Assessments, a think tank in Washington.

Within days, Mr. Gates is expected to nominate a new civilian official to oversee the service. That individual's first job will be to refocus on the Air Force's nuclear mission, its most critical job but one it had lost sight of, Gates said Thursday.

The unprecedented firings stem from two separate incidents over the past year. In August, a B-52 bomber flew from Minot Air Force Base in North Dakota to Barksdale Air Force Base in Louisiana mistakenly armed with nuclear cruise missiles. Then in March, US officials discovered that the Air Force, along with another defense agency, had accidentally sent nuclear missile nose cone fuses instead of helicopter batteries to Taiwan. The mistake was discovered 17 months later, and the fuses brought back under US control.

Gates's nominee for Air Force secretary will reportedly be Michael Donley, now a top Pentagon aide. He will have to examine the institutional culture that led to the incidents in the first place. A Pentagon investigation directed by Gates in March concluded that there were systemic problems the service had failed to address.

The new Air Force secretary may also preside over additional disciplinary action for a number of general officers and colonels involved in the incidents, according to Gates. He established an independent task force led by former Defense Secretary James Schlesinger to monitor the Air Force's efforts to solve its problems. Gates will also tour Air Force facilities this week to highlight efforts to fix the nuclear mission.

"The report makes clear that these problems and mistakes have their roots in decisions made over a period of at least 10 years," Gates said. "Nonetheless, many of the problems leading to the Minot and nose cone incidents have been known or should have been known."

The shake-up comes at a time when the Air Force is receiving much scrutiny in Washington. The recent decision to award a new tanker contract to a firm partly owned by a European consortium and not to Boeing has outraged some members of Congress. Another contract under the Air Force's Thunderbirds, a ceremonial unit that performs at air shows, had been awarded improperly, an investigation found. And Air Force officials have been clashing with others in the Pentagon over a base realignment deal that they worried would take away control of some of their own assets.

The service has also been lobbying for billions of dollars more to buy expensive weapons systems such as the F-22 stealth fighter, by highlighting threats from conventional armies such as China's. This year, it raised eyebrows when it argued for money beyond the official budget endorsed by the White House, at a time when supporting ground forces in Iraq and Afghanistan is seen as more critical. Gates has also expressed concern over the Air Force's ability to provide remote control aircraft to the wars.

Still, Ehrhard fears a double standard favoring other services over the Air Force has begun to creep into Pentagon thinking. The shipment of nuclear weapons is a serious issue, he says, but the two incidents are "administrative errors" that did not endanger the public or threaten the integrity of the US nuclear program. He worries that the Air Force has taken a big hit while other services have remained largely unscathed for more serious violations. "I think there is a balance issue here."